Plane.js

import Cartesian3 from "./Cartesian3.js";
import Check from "./Check.js";
import defined from "./defined.js";
import DeveloperError from "./DeveloperError.js";
import CesiumMath from "./Math.js";
import Matrix4 from "./Matrix4.js";

/**
 * A plane in Hessian Normal Form defined by
 * <pre>
 * ax + by + cz + d = 0
 * </pre>
 * where (a, b, c) is the plane's <code>normal</code>, d is the signed
 * <code>distance</code> to the plane, and (x, y, z) is any point on
 * the plane.
 *
 * @alias Plane
 * @constructor
 *
 * @param {Cartesian3} normal The plane's normal (normalized).
 * @param {Number} distance The shortest distance from the origin to the plane.  The sign of
 * <code>distance</code> determines which side of the plane the origin
 * is on.  If <code>distance</code> is positive, the origin is in the half-space
 * in the direction of the normal; if negative, the origin is in the half-space
 * opposite to the normal; if zero, the plane passes through the origin.
 *
 * @example
 * // The plane x=0
 * var plane = new Cesium.Plane(Cesium.Cartesian3.UNIT_X, 0.0);
 *
 * @exception {DeveloperError} Normal must be normalized
 */
function Plane(normal, distance) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.object("normal", normal);
  if (
    !CesiumMath.equalsEpsilon(
      Cartesian3.magnitude(normal),
      1.0,
      CesiumMath.EPSILON6
    )
  ) {
    throw new DeveloperError("normal must be normalized.");
  }
  Check.typeOf.number("distance", distance);
  //>>includeEnd('debug');

  /**
   * The plane's normal.
   *
   * @type {Cartesian3}
   */
  this.normal = Cartesian3.clone(normal);

  /**
   * The shortest distance from the origin to the plane.  The sign of
   * <code>distance</code> determines which side of the plane the origin
   * is on.  If <code>distance</code> is positive, the origin is in the half-space
   * in the direction of the normal; if negative, the origin is in the half-space
   * opposite to the normal; if zero, the plane passes through the origin.
   *
   * @type {Number}
   */
  this.distance = distance;
}

/**
 * Creates a plane from a normal and a point on the plane.
 *
 * @param {Cartesian3} point The point on the plane.
 * @param {Cartesian3} normal The plane's normal (normalized).
 * @param {Plane} [result] The object onto which to store the result.
 * @returns {Plane} A new plane instance or the modified result parameter.
 *
 * @example
 * var point = Cesium.Cartesian3.fromDegrees(-72.0, 40.0);
 * var normal = ellipsoid.geodeticSurfaceNormal(point);
 * var tangentPlane = Cesium.Plane.fromPointNormal(point, normal);
 *
 * @exception {DeveloperError} Normal must be normalized
 */
Plane.fromPointNormal = function (point, normal, result) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.object("point", point);
  Check.typeOf.object("normal", normal);
  if (
    !CesiumMath.equalsEpsilon(
      Cartesian3.magnitude(normal),
      1.0,
      CesiumMath.EPSILON6
    )
  ) {
    throw new DeveloperError("normal must be normalized.");
  }
  //>>includeEnd('debug');

  var distance = -Cartesian3.dot(normal, point);

  if (!defined(result)) {
    return new Plane(normal, distance);
  }

  Cartesian3.clone(normal, result.normal);
  result.distance = distance;
  return result;
};

var scratchNormal = new Cartesian3();
/**
 * Creates a plane from the general equation
 *
 * @param {Cartesian4} coefficients The plane's normal (normalized).
 * @param {Plane} [result] The object onto which to store the result.
 * @returns {Plane} A new plane instance or the modified result parameter.
 *
 * @exception {DeveloperError} Normal must be normalized
 */
Plane.fromCartesian4 = function (coefficients, result) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.object("coefficients", coefficients);
  //>>includeEnd('debug');

  var normal = Cartesian3.fromCartesian4(coefficients, scratchNormal);
  var distance = coefficients.w;

  //>>includeStart('debug', pragmas.debug);
  if (
    !CesiumMath.equalsEpsilon(
      Cartesian3.magnitude(normal),
      1.0,
      CesiumMath.EPSILON6
    )
  ) {
    throw new DeveloperError("normal must be normalized.");
  }
  //>>includeEnd('debug');

  if (!defined(result)) {
    return new Plane(normal, distance);
  }
  Cartesian3.clone(normal, result.normal);
  result.distance = distance;
  return result;
};

/**
 * Computes the signed shortest distance of a point to a plane.
 * The sign of the distance determines which side of the plane the point
 * is on.  If the distance is positive, the point is in the half-space
 * in the direction of the normal; if negative, the point is in the half-space
 * opposite to the normal; if zero, the plane passes through the point.
 *
 * @param {Plane} plane The plane.
 * @param {Cartesian3} point The point.
 * @returns {Number} The signed shortest distance of the point to the plane.
 */
Plane.getPointDistance = function (plane, point) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.object("plane", plane);
  Check.typeOf.object("point", point);
  //>>includeEnd('debug');

  return Cartesian3.dot(plane.normal, point) + plane.distance;
};

var scratchCartesian = new Cartesian3();
/**
 * Projects a point onto the plane.
 * @param {Plane} plane The plane to project the point onto
 * @param {Cartesian3} point The point to project onto the plane
 * @param {Cartesian3} [result] The result point.  If undefined, a new Cartesian3 will be created.
 * @returns {Cartesian3} The modified result parameter or a new Cartesian3 instance if one was not provided.
 */
Plane.projectPointOntoPlane = function (plane, point, result) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.object("plane", plane);
  Check.typeOf.object("point", point);
  //>>includeEnd('debug');

  if (!defined(result)) {
    result = new Cartesian3();
  }

  // projectedPoint = point - (normal.point + scale) * normal
  var pointDistance = Plane.getPointDistance(plane, point);
  var scaledNormal = Cartesian3.multiplyByScalar(
    plane.normal,
    pointDistance,
    scratchCartesian
  );

  return Cartesian3.subtract(point, scaledNormal, result);
};

var scratchPosition = new Cartesian3();
/**
 * Transforms the plane by the given transformation matrix.
 *
 * @param {Plane} plane The plane.
 * @param {Matrix4} transform The transformation matrix.
 * @param {Plane} [result] The object into which to store the result.
 * @returns {Plane} The plane transformed by the given transformation matrix.
 */
Plane.transform = function (plane, transform, result) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.object("plane", plane);
  Check.typeOf.object("transform", transform);
  //>>includeEnd('debug');

  Matrix4.multiplyByPointAsVector(transform, plane.normal, scratchNormal);
  Cartesian3.normalize(scratchNormal, scratchNormal);

  Cartesian3.multiplyByScalar(plane.normal, -plane.distance, scratchPosition);
  Matrix4.multiplyByPoint(transform, scratchPosition, scratchPosition);

  return Plane.fromPointNormal(scratchPosition, scratchNormal, result);
};

/**
 * Duplicates a Plane instance.
 *
 * @param {Plane} plane The plane to duplicate.
 * @param {Plane} [result] The object onto which to store the result.
 * @returns {Plane} The modified result parameter or a new Plane instance if one was not provided.
 */
Plane.clone = function (plane, result) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.object("plane", plane);
  //>>includeEnd('debug');

  if (!defined(result)) {
    return new Plane(plane.normal, plane.distance);
  }

  Cartesian3.clone(plane.normal, result.normal);
  result.distance = plane.distance;

  return result;
};

/**
 * Compares the provided Planes by normal and distance and returns
 * <code>true</code> if they are equal, <code>false</code> otherwise.
 *
 * @param {Plane} left The first plane.
 * @param {Plane} right The second plane.
 * @returns {Boolean} <code>true</code> if left and right are equal, <code>false</code> otherwise.
 */
Plane.equals = function (left, right) {
  //>>includeStart('debug', pragmas.debug);
  Check.typeOf.object("left", left);
  Check.typeOf.object("right", right);
  //>>includeEnd('debug');

  return (
    left.distance === right.distance &&
    Cartesian3.equals(left.normal, right.normal)
  );
};

/**
 * A constant initialized to the XY plane passing through the origin, with normal in positive Z.
 *
 * @type {Plane}
 * @constant
 */
Plane.ORIGIN_XY_PLANE = Object.freeze(new Plane(Cartesian3.UNIT_Z, 0.0));

/**
 * A constant initialized to the YZ plane passing through the origin, with normal in positive X.
 *
 * @type {Plane}
 * @constant
 */
Plane.ORIGIN_YZ_PLANE = Object.freeze(new Plane(Cartesian3.UNIT_X, 0.0));

/**
 * A constant initialized to the ZX plane passing through the origin, with normal in positive Y.
 *
 * @type {Plane}
 * @constant
 */
Plane.ORIGIN_ZX_PLANE = Object.freeze(new Plane(Cartesian3.UNIT_Y, 0.0));
export default Plane;